Boost.Context is a foundational library that provides a sort of cooperative multitasking on a single thread. By providing an abstraction of the current execution state in the current thread, including the stack (with local variables) and stack pointer, all registers and CPU flags, and the instruction pointer, a fcontext_t instance represents a specific point in the application's execution path. This is useful for building higher-level abstractions, like coroutines, cooperative threads (userland threads) or an equivalent to C# keyword yield in C++.

Boost.Coroutine provides templates for generalized subroutines which allow multiple entry points for suspending and resuming execution at certain locations. It preserves the local state of execution and allows re-entering subroutines more than once (useful if state must be kept across function calls).